Disk and tape drive data storage devices may employ thin film magnetic transducers positioned proximate a magnetic surface of a storage medium such as a hard disk or tape. Hard disk drive data storage devices typically employ thin film magnetic transducers carried on a somewhat conductive ceramic slider designed for aerodynamic suspension above a rigid rotating disk so as to position the transducer magnetic core tips as closely as possible to the magnetic surface coating of a disk.
A typical read/write head includes a magnetic core having an air gap to record magnetic transitions on the magnetic surface of the medium during a write operation and to sense such transitions during a read operation. The core is magnetically linked to a coil. Electrical current in the coil during a write operation generates magnetic flux in the core to record transitions in the surface magnetic coating of a disk or other medium. During a read operation a voltage is induced in the coil as recorded transitions pass the air gap. Insulating layers electrically isolate the coil, core and supporting structure, such as a slider, from each other.
The core defines pole tips which are exposed at a surface opposing the storage medium. In a disk drive head, for example, the pole tips are positioned on the air bearing surface of the slider. It is desirable to minimize the distance between the surface of the storage medium and the pole tips. This distance is typically maintained at or below a few micro inches. Coil electrical potential typically differs from that of the recording medium. Pole tip potential should be held close to that of the medium to prevent electrical discharge across the small air gap separating the medium surface from the pole tips. Such discharge produces electrical noise which interferes with the read operation and damages the pole tips and medium thereby reducing operational reliability. Typically coil to disk surface voltage is not near zero during write/read operations.
The impedance of the insulation separating coil and core must be high to prevent the core and pole tips from reaching coil potential. The breakdown voltage of coil to core insulation is typically below 1000 volts. Such insulation is therefore sensitive to overvoltages accidentially applied during fabrication, head installation, and shipping. Core-to-coil insulators are easily damaged during fabrication and use. For example, electrostatic charges can accumulate on the conductors of the magnetic circuits of the transducer, especially during head fabrication, and arc from coil to core and from core to support structure causing pole tip erosion and damaging the core to coil insulating layer thereby lowering coil to core impedance. Once such impedance is lowered, the core will assume coil potential, eventually resulting in damaging head to disk contact.
During fabrication and installation in the tape or disk storage device, it is desirable to monitor transducer core to coil insulator quality using impedance and breakdown voltage measurements. In state of the art thin film read/write heads, the core is accessible for such measurements exclusively at the tiny pole tips exposed on the delicate air bearing surface. Probing these tips is difficult and potentially damaging to the air bearing surface. Electrically connecting the core to an easily accessible structure such as a measuring pad is a primary objective of the present invention.